Abstract
Plant diversity is a core value of forests and is rapidly becoming a primary management goal under the threat of global environmental changes. Changing conditions, including forestry interventions, or lack of them, may endanger its preservation. Abandonment of management in forests previously subjected to a multipurpose silviculture and secondary succession is hypothesized to have altered the biodiverse Mediterranean forests in recent years and affected plant diversity. We used data in national forest inventory plots and local landscape ecology metrics from forest cartography, combined with artificial neural networks, to predict richness and Shannon diversity indices for the tree and shrub layers of several Mediterranean forest types. We found that richness and diversity depend on forest structure and on local landscape patterns, and also, though to a lesser degree, on site conditions (mainly soil pH), but not on forest intervention. In order to benefit plant diversity in the forest landscapes analyzed, forest management practices need to promote diameter variety, the presence of large trees, tree cover, variation in the height of trees and shrubs, and a heterogeneous local landscape at the stand level. Aleppo pine forests and Scots pine forests showed more consistent results in their models than cork oak and black pine forests, both of which require further research.
Highlights
Successful richness and Shannon diversity indices (Rich and ShDI) models were built for trees (Table 3) and shrubs (Table 4) for the six main forest types in each landscape units (LUs)
Our analyses suggest that plant diversity in Mediterranean forests, estimated through richness and Shannon diversity for trees and shrubs, depends on forest structure and on local landscape patterns, and, though to a lesser degree, on site conditions
The presence of large trees, tree cover, and variation in tree and shrub height were the best predictors of tree and shrub diversity, and should be carefully considered on a site-by-site basis by managers aiming at preserving/improving biodiversity under changing conditions
Summary
Biodiversity is an essential target for applied forestry, after the UnitedNations Conference on Environment and Development in Rio de Janeiro, Brazil, in 1992 [1], but major forest threats persist, and biodiversity is expected to decline in this century [2].The Mediterranean forests, with very high plant diversity (>100 tree species) and exceptionally rich in endemics [3], remain highly threatened [4,5], due to processes such as intensive agriculture, infrastructure development, tourism or urban sprawl, but due to the pervasive rural exodus that has triggered extensive transformations on the previously fine-grained cultural Mediterranean mosaics since the 1950s [6] and the overarching climate change trends [7]. Instead of leading towards rewilding or a forest transition to higher successional stages, abandonment has often led to landscape deterioration and ecosystem degradation [14], so it has been proposed that “biodiversity conservation in Mediterranean transition forests depends on finding viable ways of reversing the negative effects of rural land abandonment” [15], at landscape and stand scales. Environmental factors, such as the variable response of poor, marginal soils to abandonment [14,16], add complexity to decisions on how to manage fragile forest ecosystems in order to preserve diversity in the Mediterranean
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
